Fair Value of Financial Assets and Liabilities - Summary of Changes in Values of Derivative Liability (Detail) $ in Thousands |
9 Months Ended |
---|---|
Sep. 30, 2018
USD ($)
| |
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract] | |
Derivative Liability, Fair value, Beginning Balance | $ 25 |
Derivative Liability, Change in fair value | (22) |
Derivative Liability, Fair value, Ending Balance | $ 3 |